How much Space does a USB Flash Drive Really Have?

Tuesday, November 09, 2010

If you have ever purchased a USB flash drive, of any size, you will probably have noticed that the USBs are advertised at a certain data capacity size. Data capacities usually range from 128mb – 256 GB and can be found all over retail stores or on the internet. However upon inserting the USB flash drive into a computer USB port, the USB drive says less space available than what was advertised. This leaves quite a bit of people confused as to the actual size of a USB flash drive. Let us take a moment and examine this discrepancy and how it affects the USB consumer.

A USB flash drive is not the first form of storage to suffer from this common discrepancy. CDs, DVDs, BDs, Hard Drive, and even SSD all suffer from the same issue, but what is exactly causing the capacities not to line up? Well first we must look at the “maximum” capacity of a USB flash drive. A 1GB USB flash drive for example is generally referred to as 1,000MBs, but this number would be incorrect. A 1GB flash drive actually has 1024Mb. USBs naturally double in size as you progress up in data capacity, thus a 1GB flash drive is double the size of a 512Mb drive and a 2GB drive is double the size of a 1GB drive.

So now we know that a USB flash drive actually has more memory than advertised; now it is time to figure out where some of the memory is going. All storage devices no matter what size must reserve a small section of memory for running firmware. This firmware tells the storage device how to operate and is an essential part of the drive. It is this firmware that is the smoking gun when it comes to the discrepancy of the missing data capacity.

On average, about 5% of a devices storage capacity is reserved for this operating firmware. Unfortunately, as the size of the data capacity increases, so does the size of the space needed for the firmware. For a point of reference, a 1GB USB flash drive requires about 72Mb of space for firmware; where as a 32GB flash drive requires about 2.2GB worth of space for firmware.

So taking a look back at the original question, how much space does a USB flash drive really have? Well it depends on the size of the USB drive, but on average it is a safe bet to take off 5% of the advertised capacity and that is the realistic data capacity size.